Radio frequency (RF) front-end modules are utilized in mobile communication devices (e.g., laptops, cellular phones, tablets, etc.) to handle RF signals transmitted to the mobile communication devices and/or received by the mobile communication devices. Manufacturers and consumers of mobile communication devices continue to demand increasingly greater rates of data exchange (data rates) and the ability to handle RF signals formatted in accordance with an increasing variety of RF communication standards and RF communication specifications. As such, the RF front-end module may include RF transceiver circuitry with a plurality of different transmit chains and receiver chains in order to process the various types of RF signals. The RF front-end modules may thus include RF front-end circuitry, such as antenna switching circuitry, that allows for RF signals to be routed to the various transmit chains and receiver chains from one or more common antennas. However, modern RF communication standards, such as a Long Term Evolution (LTE) standard, present significant routing, switching, and performance challenges to RF front-end circuitry. For example, different specifications under the LTE standard may involve the use of RF signals within high frequency bands, high and frequent switching, and/or multiple RF signals. Current RF front-end circuitry capable of providing this type of switching functionality often suffers from inadequate isolation between the various chains of the RF transceiver circuitry. Microelectromechanical switches (MEMSs) are one type of switching technology known to provide high levels of isolation. Unfortunately, MEMSs can have limited lifetimes as a result of hot switching. Hot switching occurs when a switch makes a state change while RF power is incident on the switch. With regard to MEMSs, hot switching has been shown to significantly degrade the useful lifetime of a MEMS by heating, softening, and deforming the contact surfaces of the MEMS. This RF power incident during state changes of the MEMS can come, for example, from Wireless Fidelity (Wi-Fi) signals and cellular signals tuned to bands greater than 2.3 GHz. Wi-Fi signals can be particularly problematic because Wi-Fi antennas and cellullar antennas in a mobile communication device are likely to be in close proximity and tuned to similar frequencies. This allows the Wi-Fi transmission signals transmitted from the Wi-Fi antenna to be efficiently received by the cellular antenna. However, this also presents a risk of damaging the MEMS, since any significant incident power when a MEMS changes state presents a significant risk of damaging the MEMS. Furthermore, modern signal coding and multiplexing schemes may require high levels of switching as a result of on/off cycles. This presents an additional risk of damaging the MEMS. For instance, LTE-Time Division Duplex (TDD) techniques may require repetitive switching between RF transmission signals and RF receive signals. As such, the MEMS may begin to develop reliability issues due to the high number of on/off cycles, which can tend to wear out the components of the MEMS. Also, some MEMSs take longer to make a state change and may not be capable of switching between RF transmission signals and RF receive signals within a time budget specified by an LTE-TDD specification.
As such, RF front-end circuitry is needed that is capable of using MEMSs to route RF signals, but is also capable of meeting the time budgets required by high frequency LTE-TDD specifications, while reducing hot switching and wear on the MEMSs.